1. Field of the Invention
This invention concerns a diaphragm valve, and, more particularly, a diaphragm valve having an inlet sleeve and an outlet sleeve of elongated cross-sections that converge into a valve seat of elongated shape controlled by a diaphragm of elongated shape.
2. Description of Related Art
In prior art diaphragm valves, the inlet and outlet sections of the valve body converge into a substantially circular shape or any such shape that is inscribable in a square, such shape being generated by the confluence of two circular and substantially constant sleeves.
U.S. Pat. No. 4,319,737 to Waterfield discloses a valve having inlet and outlet sections of elliptical shapes that combine into a circular shape, and further having an opening in the body closed with a flange of square-inscribable shape. In general, the diaphragms of the valves in the prior art are circular and have square flanges. This causes such valves to have large sizes and considerable space requirements, particularly in the axial direction of flow. The manufacture of these valves also requires the use of a considerable amount of metal, resulting in very heavy weight and considerable costs, particularly as flow rates and inlet and outlet sleeve diameters, i.e. overall valve sizes, increase. Furthermore, particularly in hydraulically operated valves, the pressure exerted by the fluid that is piped in the pressure chamber defined by the bonnet part and the valve closing dome of the diaphragm may cause the diaphragm to bow out, particularly into the outlet sleeve port, because no counterbalancing pressure is provided, causing the so-called balloon effect. This drawback is also dependent on the considerable length of the radius of the circular diaphragm, when seen in the axial direction of the flow, and more particularly on the long axial diameter of the outlet sleeve port opening into the flow chamber, and is particularly serious in large-size valves, operating at very high flow rates and having large diaphragm surfaces. This drawback may cause the unsupported diaphragm to be damaged, thereby leading to leaks and/or opening/closing problems, because the diaphragm is only partly resilient or is not resilient at all.
In order to obviate this drawback, a rib may be provided in an intermediate position of the outlet sleeve port opening into the flow chamber, which rib is oriented in the flow direction and is substantially perpendicular to the plane tangent to the lower apex of the valve seat. This rib has, at its edge facing toward the dome of the diaphragm, a flattened surface and is appropriately curved to prevent the dome from bowing out when the latter is compressed against the valve seat. Nevertheless, this rib causes an increase of the construction complexity of the valve, as well as in the weight and cost of the valve, and does not solve the problem of the large size, in the flow direction, of prior art valves. Further, from the functional point of view, this rib leads to a possible build up of filamentary matters.